Currently, gatekeepers in most commercial IP telephone systems are implemented solely with software. Usually, a gatekeeper runs on a high-performance computer system under Windows or Unix OS. So a gatekeeper manages several subordinate gateway systems and provides bandwidth management, access control, address resolution, and zone management for the gateway systems. For each gateway registered to it, the gatekeeper has to manage it with certain resources; hence the gatekeeper is limited to its capacity. Currently, most gatekeeper software is designed to run on a single computer system, which limits the capacity of the gatekeeper. In addition, once the gatekeeper is out of service due to malfunction, calls to all gateways registered on it will be affected, resulting in severe service accident. Therefore, it is an important method to provide replaceable gatekeeper for enhancement of system reliability.